Two things: first, definitely use the Honda HCF-2 fluid - you can buy it online from Amazon or places like Handa Accessories (yes, spelled with an "a"). Second, look at your owner's manual. For my 2015 Civic, the "severe" schedule is replacing it every 25,000 miles or 40,000 km. Since it is just a drain and fill, a lot of the current fluid will remain in there when you do a drain and fill. Based on the research I've done, it looks like Honda (and other manufacturers) have lowered the number of miles between changes over time, in part because some of the problems some manufacturers have had with their CVTs. In short, based on that and the drain and fill is only replacing a portion of the fluid, I plan to do a drain and fill every 15,000 miles on mine, so every 30,000 miles I will get approximately the equivalent of a full fluid change. Sure, it will cost more and take more time, but with such a critical component as a transmission, I think it's worth it. Just my two cents.